User:Double sharp/Terbium

Terbium, ₆₅Tb

Terbium
Pronunciation	/ˈtɜːrbiəm/ ​(TUR-bee-əm)
Appearance	silvery white
Standard atomic weight Ar°(Tb)
	158.925354±0.000007 158.93±0.01 (abridged)
Terbium in the periodic table
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson – ↑ Tb ↓ Bk gadolinium ← terbium → dysprosium
Atomic number (Z)	65
Group	f-block groups (no number)
Period	period 6
Block	f-block
Electron configuration	[Xe] 4f9 6s2
Electrons per shell	2, 8, 18, 27, 8, 2
Physical properties
Phase at STP	solid
Melting point	1629 K ​(1356 °C, ​2473 °F)
Boiling point	3396 K ​(3123 °C, ​5653 °F)
Density (at 20° C)	8.229 g/cm3
when liquid (at m.p.)	7.65 g/cm3
Heat of fusion	10.15 kJ/mol
Heat of vaporization	391 kJ/mol
Molar heat capacity	28.91 J/(mol·K)
Vapor pressure P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 1789 1979 (2201) (2505) (2913) (3491)
Atomic properties
Oxidation states	0, +1, +2, +3, +4 (a weakly basic oxide)
Electronegativity	Pauling scale: 1.2 (?)
Ionization energies	1st: 565.8 kJ/mol 2nd: 1110 kJ/mol 3rd: 2114 kJ/mol
Atomic radius	empirical: 177 pm
Covalent radius	194±5 pm
Spectral lines of terbium
Other properties
Natural occurrence	primordial
Crystal structure	​hexagonal close-packed (hcp) (hP2)
Lattice constants	a = 360.56 pm c = 569.66 pm (at 20 °C)
Thermal expansion	at r.t. poly: 10.3 µm/(m⋅K)
Thermal conductivity	11.1 W/(m⋅K)
Electrical resistivity	α, poly: 1.150 µΩ⋅m (at r.t.)
Magnetic ordering	paramagnetic at 300 K
Molar magnetic susceptibility	+146000×10−6 cm3/mol (273 K)
Young's modulus	55.7 GPa
Shear modulus	22.1 GPa
Bulk modulus	38.7 GPa
Speed of sound thin rod	2620 m/s (at 20 °C)
Poisson ratio	0.261
Vickers hardness	450–865 MPa
Brinell hardness	675–1200 MPa
CAS Number	7440-27-9
History
Naming	after Ytterby (Sweden), where it was mined
Discovery and first isolation	Carl Gustaf Mosander (1843)
Isotopes of terbium
Main isotopes Decay abun­dance half-life (t1/2) mode pro­duct 157Tb synth 71 y ε 157Gd 158Tb synth 180 y ε 158Gd β− 158Dy 159Tb 100% stable

Terbium is a soft, ductile, malleable silvery-white metallic chemical element with symbol Tb and atomic number 65. It is the ninth member of the lanthanide series and is traditionally counted among the rare earths. Terbium is too reactive to be found in nature as a free element, but it is contained in many minerals, including cerite, gadolinite, monazite, xenotime, and euxenite.

Terbium always occurs naturally together with the other rare earth metals. It is one of the less common rare earth elements, making up 1.2 parts per million of the Earth's crust, though this abundance is still comparable to those of molybdenum and tungsten and is about six times that of indium, antimony, and cadmium. It was discovered by Carl Gustaf Mosander: after his successful 1841 splitting of cerium into new elements, including lanthanum and "didymium" (later found to be a mixture of praseodymium and neodymium), he turned his attention to yttrium in 1843 and likewise split out two new metals. Yttrium had been named for the Ytterby quarry in Sweden where it was originally discovered in gadolinite; since it had now been split into three parts, Mosander likewise split the name of Ytterby into three parts to name his new elements terbium and erbium. Due to later confusion, the names of terbium and erbium were later switched from Mosander's original. Even Mosander's terbium was impure; in 1878 Jean Charles Galissard de Marignac seperated out the new element gadolinium from Mosander's terbium. Highly pure terbium was not obtained until the advent of ion exchange techniques, due to the extreme similarity of the lanthanides hindering attempts at their separation.

Like most rare earth elements, terbium most readily forms the +3 oxidation state, which is the only stable state in aqueous solution, although the +4 oxidation state is known in some solid compounds. Aqueous Tb³⁺ ions are very pale pink and almost colourless; the reddish-brown Tb⁴⁺ ions are quickly reduced by water to Tb³⁺.

Terbium is used to dope calcium fluoride, calcium tungstate and strontium molybdate, materials that are used in solid-state devices, and as a crystal stabilizer of fuel cells which operate at elevated temperatures. As a component of Terfenol-D (an alloy that expands and contracts when exposed to magnetic fields more than any other alloy), terbium is of use in actuators, in naval sonar systems and in sensors. Most of the world's terbium supply is used in green phosphors. Terbium oxide is in fluorescent lamps and TV tubes. Terbium green phosphors are combined with divalent europium blue phosphors and trivalent europium red phosphors to provide "trichromatic" lighting technology, a high-efficiency white light used for standard illumination in indoor lighting.

Characteristics

Physical

Terbium is the ninth member of the lanthanide series. In the periodic table, it appears between the lanthanides gadolinium to its left and dysprosium to its right, and above the actinide berkelium. It is malleable, ductile and soft enough to be cut with a knife. It is relatively stable in air compared to the earlier, more reactive lanthanides in the first half of the lanthanide series. The 65 electrons of a terbium atom are arranged in the electron configuration [Xe]4f⁹6s²; normally, only three electrons can be removed before the nuclear charge becomes too great to allow further ionization, but in the case of terbium, the stability of the half-filled [Xe]4f⁷ configuration allows further ionization of a fourth electron in the presence of very strong oxidizing agents such as fluorine gas.

Terbium exists in two crystal allotropes with a transformation temperature of 1289 °C between them.

History

Bibliography

• Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.